Photocurrent Enhancement in Si-Ge Photodetectors by Utilizing Surface Plasmons

A circular slit-groove surface plasmon polaritons (SPPs) launcher surrounding a photodetector is employed theoretically to enhance the photocurrent of atypical Si-Ge photodetectors. The slit and grooves are designed such that the SPPs are focused at the center of the absorption layer of the photodetector to result in additional electric current. Fabry–Perot resonance condition accurately calculates the period of the groove, slit-groove distance, photodetector radius, and slit-photodetector distance. The manipulation leads to constructive interference between the incident light impinging from the top and the SPPs propagating toward the photodetector. Simulation result shows that photocurrent increases by approximately 13-fold when the SPPs are introduced.     

Autonomy,Equality, and Teaching among Aka Foragers and Ngandu Farmers of the Congo Basin

The significance of teaching to the evolution of human culture is under debate. We contribute to the discussion by using a quantitative, cross-cultural comparative approach to investigate the role of teaching in the lives of children in two small-scale societies: Aka foragers and Ngandu farmers of the Central African Republic. Focal follows with behavior coding were used to record social learning experiences of children aged 4 to 16 during daily life. “Teaching” was coded based on a functional definition from evolutionary biology. Frequencies, contexts, and subtypes of teaching as well as the identity of teachers were analyzed. Teaching was rare compared to observational learning, although both forms of social learning were negatively correlated with age. Children received teaching from a variety of individuals, and they also engaged in teaching. Several teaching types were observed, including instruction, negative feedback, and commands. Statistical differences in the distribution of teaching types and the identity of teachers corresponded with contrasting forager vs. farmer foundational cultural schema. For example, Aka children received less instruction, which empirically limits autonomous learning, and were as likely to receive instruction and negative feedback from other children as they were from adults. Commands, however, exhibited a different pattern suggesting a more complex role for this teaching type. Although consistent with claims that teaching is relatively rare in small-scale societies, this evidence supports the conclusion that teaching is a universal, early emerging cognitive ability in humans. However, culture (e.g., values for autonomy and egalitarianism) structures the nature of teaching.     

A comparison of scytonemin and its carbon analogue in terms of antioxidant properties through free radical mechanisms and conformational analysis: a DFT investigation

Scytonemin is a UV absorbing sheath pigment synthesized uniquely by cyanobacteria. Its biological features has attracted interest ecologically (in microbial mat systems), medically (for therapeutic activity) and astrobiologically (as a key biomarker). Recently, a carbon analogue of scytonemin, in which two nitrogen atoms are replaced by carbon atoms was synthesized to elucidate the origin of biological activity by comparison with scytonemin. In this work, their structural/conformational aspects and relative antioxidant capacity are compared making use of DFT calculations to provide insight about the similarities and differences between the two. The carbon analogue of scytonemin, isoelectronic with scytonemin, has the same structural skeleton and a similar potential energy surface but the hydrogens on the carbons that replace the nitrogens cause the phenolic rings to rotate out of the plane which is obseved for scytonemin. Thermochemically, the carbon analogue of scytonemin prefers the same radical scavenging mechanism scytonemin does, the HAT mechanism, and has a lower homolytic bond dissociation enthalpy for the OH group than that of scytonemin and other known antioxidants like ascorbic acid. The carbon analogue of scytonemin is suggested to be a novel synthetic antioxidant.     

Prenatal haloperidol alters the expression of DNA polymerases in brain regions of neonate rats

1. Previous studies have reported a marked reduction in the [3H]thymidine incorporation in forebrain after administration of a dopamine antagonist such as haloperidol. 2. We have investigated the possibility that the expression levels of genes related to DNA metabolism could be altered by haloperidol treatment. 3. By Northern blot analysis, we have studied the steady-state mRNA levels for genes involved in DNA metabolism, in neonate rat mesencephalon and forebrain, after chronic prenatal blockade of dopamine receptors with haloperidol. 4. We found that the expression levels for DNA polymerases alpha and beta were clearly reduced in forebrain by haloperidol treatment. On the contrary, the expression of DNA polymerase beta was increased in mesencephalon. 5. Our results suggest that dopamine receptors occupancy may be a critical factor in controlling cell proliferation during brain development, through a mechanism(s) involving changes in the expression of DNA polymerases.     

Effects of NaCl and iso-osmotic PEG stress on growth,osmolytes accumulation and antioxidant defense in cultured sugarcane cells

In order to discriminate between the ionic and osmotic components of salt stress, sugarcane (Saccharum officinarum L. cv. Co 86032) calli were cultured on media containing NaCl or polyethylene glycol (PEG) 8000 that exerted the same osmotic pressure (−0.7 MPa). PEG stress exposure for 15 days led to significant growth reduction and loss in water content than salt stressed and control tissues. Osmotic adjustment (OA) was observed in callus tissues grown on salt, but was not evident in callus grown on PEG. Oxidative damage to membranes, estimated in terms of accumulation of thiobarbituric acid reactive substances-TBARS and electrolytic leakage was significantly higher in both the stressed calli than the control however, the extent of damage was more in the PEG stressed calli. The stressed callus tissues showed inhibition of ascorbate peroxidase activity, while catalase activity was increased. These results indicate sensitivity of cells to PEG-mediated stress than salt stress and differences in their OA to these two stress conditions. The sensitivity to the osmotic stress indicate that expression of the stress tolerance response requires the coordinated action of different tissues in a plant and hence was not expressed at the cellular level.     

Effect of domestic cattle on the condition of female white-tailed deer in southern pine-bluestem forests,USA

Effect of domestic cattle stocking on the nutritional condition of white-tailed deerOdocoileus virginianus (Zimmermann, 1780) was assessed using physiological indices of collected specimens. Three study areas were delineated in McCurtain County, Oklahoma (heavy cattle stocking), and Howard (moderate to light cattle stocking) and Pike (no cattle stocking) counties, Arkansas that were similar with respect to soils and vegetation but differed with respect to cattle stocking rate. Female white-tailed deer were collected from study areas in February and August 1987–1988 to assess nutritional condition. Deer collected from study areas exposed to cattle grazing in February had lower carcass weights, fat attributes (femur marrow and kidney fat), and reproductive rates (fetuses/doe) than deer that were not exposed to cattle grazing. In August, deer collected from the moderate cattle area had heavier eviscerated carcass weights, serum glucose, albumin, and albumin/globulin ratios than deer collected from the heavy cattle area. Results suggest that if cattle are removed from managed forests in winter, nutritional condition of deer would be improved because of reduced competition for food.     

High T cell epitope sharing between two HLA-B27 subtypes (B*2705 and B*2709) differentially associated to ankylosing spondylitis.

HLA-B*2705 is strongly associated with ankylosing spondylitis (AS) and reactive arthritis. In contrast, B*2709 has been reported to be more weakly or not associated to AS. These two molecules differ by a single amino acid change: aspartic acid in B*2705 or histidine in B*2709 at position 116. In this study, we analyzed the degree of T cell epitope sharing between the two subtypes. Ten allospecific T cell clones raised against B*2705, 10 clones raised against B*2703 but cross-reactive with B*2705, and 10 clones raised against B*2709 were examined for their capacity to lyse B*2705 and B*2709 target cells. The anti-B*2705 and anti-B*2703 CTL were peptide dependent as demonstrated by their failure to lyse TAP-deficient B*2705-T2 transfectant cells. Eight of the anti-B*2705 and five of the anti-B*2703 CTL clones lysed B*2709 targets. The degree of cross-reaction between B*2705 and B*2709 was donor dependent. In addition, the effect of the B*2709 mutation (D116H) on allorecognition was smaller than the effect of the other naturally occurring subtype change at this position, D116Y. These results demonstrate that B*2705 and B*2709 are the antigenically closest HLA-B27 subtypes. Because allospecific T cell recognition is peptide dependent, our results imply that the B*2705- and B*2709-bound peptide repertoires are largely overlapping. Thus, to the extent to which linkage of HLA-B27 with AS is related to the peptide-presenting properties of this molecule, our results would imply that peptides within a relatively small fraction of the HLA-B27-bound peptide repertoire influence susceptibility to this disease.